A global human rights report released by the U.S. has singled out Syria's civil war as a tragedy that "stands apart in its scope and human cost", according to BBC News.
The U.S. said a chemical weapons attack in Syria that it says killed 1,429 was "one of many horrors" in the war.
The annual State Department review also noted the increased crackdown elsewhere on protesters and civil society groups.
The report cited official persecution of dissidents in Ukraine, Venezuela, Turkey and China in 2013.
The review known as the Country Reports on Human Rights Practices includes indictments of countries in every corner of the world. But it saved its harshest condemnation for the government of Syria, where well over 100,000 people have been killed and millions more forced to flee since March 2011.
It cites the August 21, 2013 chemical weapons attack on Ghouta, an agricultural belt around Damascus, as one of "many horrors in a civil war filled with countless crimes against humanity, from the torture and murder of prisoners to the targeting of civilians with barrel bombs and Scud missiles".
In remarks after the release of the report on Thursday, Secretary of State John Kerry also condemned the government of Ukraine for the recent violence against protesters.
"In Ukraine, as we all just saw in real time in the last days, tens of thousands took to the streets... to demonstrate again the power of people to be able to demand a more democratic and accountable governance, and to stand up even against those who would sniper from roofs and take their lives in the effort to have their voices heard," Kerry told reporters.
He described Ukraine as one example of a nation in which public backlash against corruption and overbearing governments has been further inflamed by official violence.
Ukraine's ex-President Viktor Yanukovych has fled the capital after months of unrest.
The report criticizes Yanukovych's government for parliamentary elections that did not meet international standards for fairness or transparency, security forces beating protesters during a peaceful 30 November demonstration, and a general crackdown on the country's news media.
Kerry also criticized the government of Venezuela, where a crackdown on anti-government protests this month left at least a dozen people dead.
The report gave poor marks to both former Egyptian President Mohammed Morsi and current interim government leader Field Marshal Abdul Fattah al-Sisi.
Also, Assistant Secretary of State Uzra Zeya said Iran had seen "little meaningful improvement" in its human rights record since the election last year of President Hassan Rouhani.
Other alleged human rights abuses and developments called out by the U.S. in the review include:
-Selective use of a law against "extremism" in Russia and persecution of government critics, religious minorities, and gays and lesbians
-Turkey's jailing of as many as 73 journalists charged under an anti-terror law
-The alleged beating and torture by security forces in Belarus of protesters and detainees
-Lapses in labor fire safety standards in Bangladesh, as the collapse of a factory building killed more than 1,000 garment workers
-Anti-gay violence and official anti-gay discrimination in Nigeria and Uganda
-A "state-directed crackdown on activists and suppression of political dissent and public advocacy" in China.